Author: Matt Martinich
Posted: November 8th, 2013
Double affiliation primarily occurs when two or more religious groups claim the same individuals as members. Two or more religious groups claim the same individual as a result of individuals changing their religious affiliation and joining another religious group without removing their membership in their previously-affiliated religious group. In the most severe cases, double affiliation results in the summation of the number of members in each religious group surpassing the total population of a country, specifically in locations where several proselytizing faiths comprise a sizable percentage of the population and exhibit high competition for converts within a small target population such as in Oceania.
Religion researchers have documented instances where the total number of religious practitioners surpasses the country's population in some East Asian countries where there is a high degree of syncretism between traditional religious groups. For example, in Japan the number of religious members totals 206 million - nearly twice the size of the Japanese population - due to most the population doubly affiliating as Shinto and Buddhist. Cultural conditions that rationalize some East Asians to identify as a member of two or more religious groups is chiefly responsible for double affiliation phenomena in East Asia whereas two or more religious groups claiming the same individuals regardless of the current self-affiliation of members on religious organization records is primarily responsible for double affiliation phenomena in Oceania and other locations where there is high competition for converts among several prominent proselytizing groups. Consequently, religious data on the Japanese census indicates nearly twice as many members of religious groups than the actual Japanese population whereas religious data on the censuses of several Polynesian countries indicates as many religious practitioners as the number of inhabitants in the country. Many governments do collect religious affiliation data on populations within their respective countries, resulting in researchers relying on faith-reported membership totals to ascertain the religious demographic characteristics of a particular country or location. Due to different faiths counting the same individuals as members, double affiliation creates challenges for religion and sociology researchers in determining the true religious makeup of a country.
In the LDS Church, double affiliation most commonly occurs when converts actively participated in another religious group prior to baptism in the LDS Church. The former religious group may continue to count the active LDS convert as a member due to similar membership guidelines as the LDS Church that retain members regardless of self-affiliation and activity status, resulting in exaggerated membership totals for the other religious group. However, it is more common for LDS converts to stop attending LDS services and either return to their previous religious group, join another religious group, or stop attending religious services altogether. This results in inflated membership totals for the LDS Church and presents an inaccurate picture of the size of the Church. The LDS Church does not remove disaffiliated members from its records unless members are excommunicated or resign membership. As the vast majority of inactive Latter-day Saints who currently attend another religious group do not get excommunicated or resign membership, the Church continues to count these members on its official totals regardless of their current religious affiliation and activity status.
The LDS Church in Oceania experiences some of its most severe cases of double affiliation. In Tonga, official LDS membership statistics indicate that there were 53,449 members as of year-end 2006 whereas the 2006 Tongan census reported only 17,109 self-identified Latter-day Saints,  or 32% of membership reported by the LDS Church. At year-end 2011, nominal LDS membership constituted 56% of the national population but the most recent census statistic reports that Latter-day Saints comprise only 17% of the national population. 2006 Tongan census totals indicate that the population self-identifies as 37% Free Wesleyan, 17% Latter-day Saint, 16% Roman Catholic, 11% Free Church of Tonga, 7% Church of Tonga, 3% Tokaikolo, and 9% other denominations and religions. Nearly all census-reported Latter-day Saints in Tonga appear active considering the total number of Latter-day Saints on the 2006 census was one-third of the official church-reported membership at the time and member activity rates in Tonga are approximately 30-35% of nominal membership. Double affiliation also occurs in Latin America and Europe where self-reported Latter-day Saints on censuses constitute less than half of church-reported membership in virtually every country. Many nominal Latter-day Saints in these nations were unretained converts that are doubly affiliated with a traditional religious group such as the Catholic Church or another proselytizing group such as evangelicals, Seventh Day Adventists, or Jehovah's Witnesses.
Doubly affiliated Latter-day Saints that actively engage in another religious group are challenging to reactivate due to their current social and religious connections outside the Church but nonetheless do not present an insurmountable obstacle as they can return to self-affiliation in the LDS Church. LDS missionaries, leaders, and members need to emphasize unique doctrinal teachings and theological positions to help curb against the loss of some Latter-day Saints to other Christian denominations and safeguard against convert attrition.
 "Japan," International Religious Freedom Report 2010, 17 November 2010. http://www.state.gov/g/drl/rls/irf/2010/148871.htm
 Zoll, Rachel, "The Numbers Game: Accuracy Elusive When Counting Followers of Religion," Shawnee News Star Online, November 10, 2001.
 "Social characteristics - Religion," Population Census 2006 - Tonga Department of Statistics, retrieved 24 December 2010. http://www.spc.int/prism/country/to/stats/Census06/social/religion.htm
 "Tonga 2006 Census of Population and Housing, Volume 2: Analytical Report," Tongan Statistics Department, 2008. http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDoQFjAB&url=http%3A%2F%2Fwww.spc.int%2Fprism%2Ftonga%2Findex.php%2Fpopulation-censuses%2F2006-census%2Fdoc_download%2F45-tonga-2006-analytical-census-report-vol2&ei=W_usUJyCMuTuyAHO6IH4DQ&usg=AFQjCNHSBsyhdEbj9SBiaFweN_fPROytmQ